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/*
* Copyright (c) 2004-2005, 2010-2018 Todd C. Miller <Todd.Miller@sudo.ws>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* This is an open source non-commercial project. Dear PVS-Studio, please check it.
* PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
*/
#include <config.h>
#include <sys/types.h>
#if defined(HAVE_DECL_SECCOMP_SET_MODE_FILTER) && HAVE_DECL_SECCOMP_SET_MODE_FILTER
# include <sys/prctl.h>
# include <asm/unistd.h>
# include <linux/filter.h>
# include <linux/seccomp.h>
#endif
#include <errno.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#ifdef HAVE_SPAWN_H
#include <spawn.h>
#endif
#ifdef HAVE_STRING_H
# include <string.h>
#endif /* HAVE_STRING_H */
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif /* HAVE_STRINGS_H */
#ifdef HAVE_WORDEXP_H
#include <wordexp.h>
#endif
#if defined(HAVE_SHL_LOAD)
# include <dl.h>
#elif defined(HAVE_DLOPEN)
# include <dlfcn.h>
#endif
#include "sudo_compat.h"
#include "pathnames.h"
#ifdef HAVE___INTERPOSE
/*
* Mac OS X 10.4 and above has support for library symbol interposition.
* There is a good explanation of this in the Mac OS X Internals book.
*/
typedef struct interpose_s {
void *new_func;
void *orig_func;
} interpose_t;
# define FN_NAME(fn) dummy_ ## fn
# define INTERPOSE(fn) \
__attribute__((__used__)) static const interpose_t interpose_ ## fn \
__attribute__((__section__("__DATA,__interpose"))) = \
{ (void *)dummy_ ## fn, (void *)fn };
#else
# define FN_NAME(fn) fn
# define INTERPOSE(fn)
#endif
/*
* Dummy versions of the exec(3) family of syscalls. It is not enough to
* just dummy out execve(2) since many C libraries do not call the public
* execve(2) interface. Note that it is still possible to access the real
* syscalls via the syscall(2) interface, but that is rarely done.
*/
#define DUMMY_BODY \
{ \
errno = EACCES; \
return -1; \
}
#define DUMMY1(fn, t1) \
__dso_public int \
FN_NAME(fn)(t1 a1) \
DUMMY_BODY \
INTERPOSE(fn)
#define DUMMY2(fn, t1, t2) \
__dso_public int \
FN_NAME(fn)(t1 a1, t2 a2) \
DUMMY_BODY \
INTERPOSE(fn)
#define DUMMY3(fn, t1, t2, t3) \
__dso_public int \
FN_NAME(fn)(t1 a1, t2 a2, t3 a3) \
DUMMY_BODY \
INTERPOSE(fn)
#define DUMMY6(fn, t1, t2, t3, t4, t5, t6) \
__dso_public int \
FN_NAME(fn)(t1 a1, t2 a2, t3 a3, t4 a4, t5 a5, t6 a6) \
DUMMY_BODY \
INTERPOSE(fn)
#define DUMMY_VA(fn, t1, t2) \
__dso_public int \
FN_NAME(fn)(t1 a1, t2 a2, ...) \
DUMMY_BODY \
INTERPOSE(fn)
/*
* Standard exec(3) family of functions.
*/
DUMMY_VA(execl, const char *, const char *)
DUMMY_VA(execle, const char *, const char *)
DUMMY_VA(execlp, const char *, const char *)
DUMMY2(execv, const char *, char * const *)
DUMMY2(execvp, const char *, char * const *)
DUMMY3(execve, const char *, char * const *, char * const *)
/*
* Non-standard exec(3) functions and corresponding private versions.
*/
#ifdef HAVE_EXECVP
DUMMY3(execvP, const char *, const char *, char * const *)
#endif
#ifdef HAVE_EXECVPE
DUMMY3(execvpe, const char *, char * const *, char * const *)
#endif
#ifdef HAVE_EXECT
DUMMY3(exect, const char *, char * const *, char * const *)
#endif
/*
* Not all systems support fexecve(2), posix_spawn(2) and posix_spawnp(2).
*/
#ifdef HAVE_FEXECVE
DUMMY3(fexecve, int , char * const *, char * const *)
#endif
#ifdef HAVE_POSIX_SPAWN
DUMMY6(posix_spawn, pid_t *, const char *, const posix_spawn_file_actions_t *, const posix_spawnattr_t *, char * const *, char * const *)
#endif
#ifdef HAVE_POSIX_SPAWNP
DUMMY6(posix_spawnp, pid_t *, const char *, const posix_spawn_file_actions_t *, const posix_spawnattr_t *, char * const *, char * const *)
#endif
/*
* system(3) and popen(3).
* We can't use a wrapper for popen since it returns FILE *, not int.
*/
DUMMY1(system, const char *)
__dso_public FILE *
FN_NAME(popen)(const char *c, const char *t)
{
errno = EACCES;
return NULL;
}
INTERPOSE(popen)
#if defined(HAVE_WORDEXP) && (defined(RTLD_NEXT) || defined(HAVE_SHL_LOAD) || defined(HAVE___INTERPOSE))
/*
* We can't use a wrapper for wordexp(3) since we still want to call
* the real wordexp(3) but with WRDE_NOCMD added to the flags argument.
*/
typedef int (*sudo_fn_wordexp_t)(const char *, wordexp_t *, int);
__dso_public int
FN_NAME(wordexp)(const char *words, wordexp_t *we, int flags)
{
#if defined(HAVE___INTERPOSE)
return wordexp(words, we, flags | WRDE_NOCMD);
#else
# if defined(HAVE_DLOPEN)
void *fn = dlsym(RTLD_NEXT, "wordexp");
# elif defined(HAVE_SHL_LOAD)
const char *name, *myname = _PATH_SUDO_NOEXEC;
struct shl_descriptor *desc;
void *fn = NULL;
int idx = 0;
name = strrchr(myname, '/');
if (name != NULL)
myname = name + 1;
/* Search for wordexp() but skip this shared object. */
while (shl_get(idx++, &desc) == 0) {
name = strrchr(desc->filename, '/');
if (name == NULL)
name = desc->filename;
else
name++;
if (strcmp(name, myname) == 0)
continue;
if (shl_findsym(&desc->handle, "wordexp", TYPE_PROCEDURE, &fn) == 0)
break;
}
# else
void *fn = NULL;
# endif
if (fn == NULL) {
errno = EACCES;
return -1;
}
return ((sudo_fn_wordexp_t)fn)(words, we, flags | WRDE_NOCMD);
#endif /* HAVE___INTERPOSE */
}
INTERPOSE(wordexp)
#endif /* HAVE_WORDEXP && (RTLD_NEXT || HAVE_SHL_LOAD || HAVE___INTERPOSE) */
/*
* On Linux we can use a seccomp() filter to disable exec.
*/
#if defined(HAVE_DECL_SECCOMP_SET_MODE_FILTER) && HAVE_DECL_SECCOMP_SET_MODE_FILTER
/* Older systems may not support execveat(2). */
#ifndef __NR_execveat
# define __NR_execveat -1
#endif
static void noexec_ctor(void) __attribute__((constructor));
static void
noexec_ctor(void)
{
struct sock_filter exec_filter[] = {
/* Load syscall number into the accumulator */
BPF_STMT(BPF_LD | BPF_ABS, offsetof(struct seccomp_data, nr)),
/* Jump to deny for execve/execveat */
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_execve, 2, 0),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_execveat, 1, 0),
/* Allow non-matching syscalls */
BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW),
/* Deny execve/execveat syscall */
BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ERRNO | (EACCES & SECCOMP_RET_DATA))
};
const struct sock_fprog exec_fprog = {
nitems(exec_filter),
exec_filter
};
/*
* SECCOMP_MODE_FILTER will fail unless the process has
* CAP_SYS_ADMIN or the no_new_privs bit is set.
*/
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == 0)
(void)prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &exec_fprog);
}
#endif /* HAVE_DECL_SECCOMP_SET_MODE_FILTER */
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